As its name implied, the Swelling Solution could make part of an object swell up.
Sean did not know what it was used for, only that, like most potions—
If brewed or used incorrectly, it could lead to serious consequences.
For example, when second-year students were making Swelling Solution, Harry had thrown a firework into Goyle's cauldron, distracting everyone.
Wherever the potion splashed, people's arms, noses, eyes, and so on swelled grotesquely.
So Sean carefully watched Professor Snape's every movement while the Quill of Acceptance scratched away beside him.
Grind two spoonfuls of dried nettle, grind three pufferfish eyes, add both ground mixtures to the cauldron, heat for twenty seconds, wave the wand...
Professor Snape's instructions often did not follow the textbook, and he even made extensive changes to certain steps—
If any young wizard dared to lose focus for even a moment and followed the book instead, an accident could easily occur.
Perhaps that was one reason Professor Snape was so stern, even intimidating, toward the young wizards.
"If your empty brains have finally managed to stuff in some knowledge,"
Professor Snape waved his wand, and the finished potion was poured into crystal bottles.
He swept his gaze around the room. The young wizards were silent as mice.
"Then pair up and get started!"
The classroom immediately filled with clanging sounds as the young wizards began brewing, trembling all the while.
After a while, the brewing reached its final stage.
"...Process the final ingredient, then brew until a layer of white foam appears on the surface of the potion..."
Justin checked the notes, looking even more nervous than Sean, who was stirring the cauldron.
Professor Snape was still making his rounds to prevent another accident.
But when he reached Sean and Justin, his steps paused.
He casually glanced at